Screen-tightening apparatus



C. D. GREENINGER SCREEN-TIGHTENING APPARATUS Sept. so, ass

2 Sheets-Sheet Filed Oct. 20, 1967 FIG. 7

FIG. 6

CARROLL D. GREENINGER wvayrm BUG/(HORN, BLORE, KLAROU/ST a SPAR/(MAN ATTORNEYS United States Patent 3,469,695 SCREEN -TIGHTENING APPARATUS Carroll D. Greeninger, Rte. 2, Box 42, Astoria, Oreg. 97103 Filed Oct. 20, 1967, Ser. No. 676,969 Int. Cl. B07b 1/28 US. Cl. 209-403 14 Claims ABSTRACT OF THE DISCLOSURE A screen cloth in a vibrating screen apparatus is held in place between two freely rotatable members pivotally attached to the sides of the screen frame. These rotatable members are adapted to selectively grip hooked margins of the screen cloth as each such member is rotated in a predetermined direction. Means are provided for applying leverage to the rotatable members for rotating the same to a desired position whereby tension is applied to the cloth, after which the rotatable members are locked in position.

Background of the invention A vibrating screen apparatus, of the type used for sorting or classifying crushed rock and the like, conventionally employs a screen cloth in the form of a steel mesh having spaces between its crossed elements through which selected rock particles may pass. Such a screen cloth may be quite heavy. For example, in a typical instance a cloth consists of interwoven one-quarter inch steel rods or bars and is called upon to separate tons of rock or other material. The screen cloth must be substantially rigidly supported Within a vibrating frame of the apparatus in order to provide optimum vibrational effectiveness, while preventing undue flexure of such cloth as would result in premature failure.

Screen cloths are usually attached to a screen frame by means of a plurality of tensioning plates or clamps for engaging the mar-gin of the screen, and which are drawn up against the frame by means of adjustable screws or bolts for supplying the tensioning force. When a screen cloth is to be installed or replaced, the adjustment of a large number of bolts is necessary, and can become quite tedious and time consuming. For example, as much as twenty-four hours may be required to make a changeover from one screen cloth to another, and, in a typical heavy duty operation it may be necessary to replace a screen cloth three to four times a month.

Summary of the invention According to the present invention, a freely rotatable member is pivotally secured to each lateral side of the screen frame, each such member including an outwardly directed screen-engaging edge rotatable into hooked relation with a hooked margin of the screen cloth. Means are provided for applying leverage to the rotatable member for rapidly rotating the same to a desired position whereby the screen cloth is placed under predetermined tension. Then, such rotatable member is locked in the tensioned position.

According to a preferred embodiment, each such rotatable member comprises a slotted pipe journaled within an outer pipe, the latter being substantially integral with a lateral side of the screen frame. The outer pipe is also slotted to allow passage of the margin of the secreen cloth into hooked relation with the slot in the inner pipe. Gear means are mounted on the inner pipe and form a part of means for applying leverage for rotating such inner pipe to a desired screen-tensioning position. Thereafter the gear means is locked in place.

The installation or replacement of a heavy screen cloth can be accomplished quickly and with a minimum of labor according to the present invention, requiring no tedious and time-consuming setting and adjustment of a plurality of screws or bolts. Replacement or installation time of a screen cloth is thereby reduced to an hour or two at most as compared with many hours or days as heretofore frequently required.

It is accordingly an object of the present invention to provide an improved screen tightening apparatus which is easily operable in a short period of time for installation and removal of heavy screen cloths.

It is another object of the present invention to provide an improved screen tightening apparatus which does not require the manipulation of a plurality of screws or bolts for installation or removal of a screen cloth.

It is another object of the present invention to provide an improved screen tightening apparatus for securing a heavy duty screen cloth in place by rotation and locking of a rotatable member.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements.

Drawings FIG. 1 is a plan view of a screen apparatus employing screen tightening apparatus according to the present invention;

FIG. 2 is a side view of the FIG. 1 apparatus;

FIG. 3 is an end view of the FIG. 1 apparatus;

FIG. 4 is a detailed cross-sectional view of a rotatable screen-engaging member according to the present invention, taken at 4-4 in FIG. 1, including means for applying leverage for rotating such rotatable member and locking the same in place;

FIG. 5 is a cross-sectional view of a rotatable screenengaging member according to the present invention, illustrating alternative means for locking such rotatable memher in place;

FIG. 6 is a cross section of a rotatable screen-engaging member according to the present invention, taken at 6-6 in FIG. 1, illustrating a first hanger means for supporting such member;

FIG. 7 is a cross section of the same rotatable member, taken at 7-7 in FIG. 1, illustrating a second hanger means for supporting such rotatable member;

FIG. 8 is a cross sectional view of a rotatable screenengaging member accOrding to the present invention illustrating engagement of a driving gear means by a spanner wrench for applying leverage thereto;

FIG. 9 is a cross sectional view of a rotatable screenengaging member according to the present invention illustrating an alternative hydraulically operated leverageapplying mechanism therefor;

FIG. 10 is a cross sectional view of an alternative rotatable screen-engaging rotatable member according to the present invention including means for applying leverage thereto; and

FIG. 11 is a side view of the FIG. 10 embodiment taken at 11-11 in FIG. 10.

Detailed description Referring to the drawings, and particularly to FIGS. 1 through 8, a vibrating screen apparatus according to the present invention includes a frame 10 having lateral side members 12 and 14 separated and maintained in parallel relation by cross members 16 secured therebetween. Each lateral side member comprises a vertical side wall 18 and a plurality of spaced vertical braces 20 joined as by welding to each side wall 18. Substantially integrally included in or attached to each lateral side wall is a first cylindrical pipe member 22 extending longitudinally along the side wall and suitably welded within a longitudinal aperture in the side wall so that a diameter of the pipe member substantially coincides with the plane or extended location of wall 18. Each brace 20 is also shaped to receive pipe member 22, with the pipe member also being Welded thereto in supporting relation. It is observed that braces 20 support not only pipe member 22, but also support the portion of wall 18 above the pipe member 22 in alignment with the lower portion of wall 18. It is understood that frame is suitably located in an apparatus including a drive motor or the like for imparting vibrational movement to the frame.

The frame provides support for a screen cloth 24 located centrally and substantially horizontally in the frame between lateral side members 12 and 14 and above cross members 16. Risers 26 extend from cross member 16 and support the underside of the screen cloth for arching the screen cloth 24 slightly to decrease flexure and undesired vertical vibration of the screen cloth.

The screen cloth 24 is ordinarily quite heavy, especially in the case of heavy duty sorting and classifying operations, a typical screen being formed of interwoven one-quarter inch steel rod. A screen adapted for cooperation with the apparatus of the present invention is suitably bent at the lateral side edges thereof to provide an upturned, or hooked, margin 28 along each lateral side edge of the screen cloth. The margin is turned at an angle of at least 90 degrees with respect to the central, substantially horizontal plane of screen cloth 24, and is desirably bent somewhat more than 90 degrees whereby to provide a hook-like configuration. Alternatively, a steel binder strip may be welded along each lateral side edge of the screen cloth for providing the desired hooked configuration.

Each pipe member 22 is provided with a longitudinal slot 30 for receiving therethrough the hooked margin of the screen cloth. Slot 30 faces inwardly of the lateral side members towards the central position of the screen cloth 24, and downwardly, so that the upturned hooked margin of the screen cloth may be conveniently received therewithin. Suitably, the slot 30 extends for approximately 90 degrees around the circumference of each pipe member 22, starting at the lower portion of wall 18.

Within each pipe member 22 is located a rotatable member, here taking the form of an inner cylindrical pipe Inner pipe member 32 is provided with a longitudinal I slot 44 which has about the same circumferential extent ceiving in hooked relation the hooked margin of the screen cloth.

The screen cloth 24 is suitably inserted in the apparatus from one end thereof, as from the left side in FIGS. 1 and 2, with the upraised hooked margins 28 being inserted through slot 30 in each pipe member 22, and with each such hooked margin extending in loosely hooked relation around the outwardly directed edge of the slot 44 in each inner pipe member 32. Thus slot 30 in each outer pipe member provides access for the screen cloth to the inner pipe member. Then, the inner pipe members are rotated in opposite directions, in a manner hereinafter more fully member 32, journaled for rotation within pipe member v 22. Inner cylindrical pipe member 32 is thus pivotally secured for rotation about its own axis within pipe member 22, which is in turn secured to the frame along a lateral side thereof adjacent a hooked margin of the screen cloth. While the inner pipe member 32 is rotatable substantially concentrically Within pipe member 22, it is understood that the inner diameter of pipe member 22 does not necessarily provide a complete bearing surface for pipe member 32, inasmuch as the latter may be somewhat loosely received within the former. Each inner pipe member 32 is also suitably hung within the outer pipe member, for example by means of a hanger comprising a screw 34 threadably received in a tapped hole in the inner pipe member 32 and extending through a circumferential slot 36 in the outer pipe member. (See FIG. 6.) The screw head rests upon a rubber washer 38 and a washer 40 having a diameter larger than the width'of slot 36 so that screw 34 supports the inner pipe member 32, while also permitting rotation thereof as the screw head slides around slot 36. Wall 18 is apertured at 42 so that the head of screw 34 and the washers retained thereby may pass through wall 18 as they move along slot 36. Such a' screw 34 is suitably located in a slot 36 at either end of each pipe member 22 to provide hanger means for pipe member 32, whereby pipe member 32 will be less apt to drop through aperture 30 in the outer pipe member 32 when in a non-tensioning position.

described, to grip the screen cloth and place the screen cloth 24 under the desired tension. For example, the left hand inner pipe member 32, as viewed in FIG. 3, is rotated in a clockwise direction, and the right hand inner pipe member 32 is rotated in a counterclockwise direction. As will be observed, the inner pipe members are easily rotatable, being pivotally secured within the lateral side members, and no laborious setting of bolts is required for tightening of the screen cloth.

The rotatable inner pipe members are rapidly turned into tension-applying position employing means for applying leverage to each such rotatable member. This means for applying leverage suitably includes gear means 46 secured to each inner pipe member, spur gear means 48 meshing the gear means 46, and lever-engaging means for turning the spur gear means. Gear means 46 here comprises plural rack gear segments joined to each inner pipe member at the periphery thereof in the direction toward the outside of the lateral side member, that is, the side thereof away from screen cloth 24. Such rack gear segments are joined as by welding to the periphery of each pipe member 32 at spaced locations therealong, while outer pipe means 22 is apertured at such locations to provide for passage of the rack gear segments so that the rack gear segments are drivable from outside the outer pipe member. Such aperture in the outer pipe member is numbered 50 in FIG. 4. The upper portion of wall 18 is also provided with an aperture 52 at the location of each rack gear segment so the same may pass through wall 18 to the extent necessary as the inner pipe member turns. Cover means 53,secured to the frame side members, extend inwardly from the wall of each side frame member above apertures 50 and 52 to protect apertures 50 and 52 and the gear means from rock and the like which may be supported on the screen cloth.

A bracket 54is suitably joined to the frame, and in particular to pipe member 22, at either longitudinal side of each aperture 50, and such brackets provide bearing means for journaling a shaft 56 carrying spur gear means 48. The shaft 56 is suitably provided with lever engageable means comprising a square end 58 on at least one end thereof for receiving wrench-ended lever means 60 having a socket 62 matching the square shaft end 58. The wrench-ended lever means 60 is suitably of considerable length, and is shown broken in FIG. 1 for ease of illustration. Preferably, the arm thereof is of extended length so that a downward force on the end of such arm will easily and rapidly rotate spur gear means 48 in a counterclockwise direction as viewed in FIG. 4. counterclockwise movement of spur gear means 48 drives gear-means 46 and inner pipe member 32 in a clockwise direction within a predetermined arc for drawing the upturned hooked margin 28 of screen cloth 24 to the left as indicated by the arrow in FIG. 4. It is apparent end wrench could be employed in place of lever means 60, if so desired.

Preferably, a pair of lever arm-s is applied to a pair of spur gears, meshing with spaced rack gear segments, at the same time, so that the same may suitably be operated by One man standing therebetween. When the desired degree of tension is applied to screen cloth 24, the gear means may be locked by placing a block in the form of a loose gear 57 in engagement with both gear means 46 and 48 as indicated in FIG. 4, the loose gear providing locking means. Alternatively, a pawl or detent 64 is pivoted on frame side member wall 18, as illustrated in FIG. 5, and cooperates with the teeth of spur gear means 48 in ratchet fashion to provide locking means for locking the same at the desired tensioning position.

An alternative construction is illustrated in FIG. 8 wherein the lever engageable means provided by spur gear means 48 comprises a cylindrical section 66 having a plurality of wrench-engaging apertures 68. These apertures are engageable by a long-handled spanner wrench 70 for turning the spur gear means 48 in a counterclockwise direction.

In the case of either of the foregoing embodiments, the rotatable inner pipe member 32 may advantageously be rapidly turned to apply the desired degree of tension to screen cloth 24, after which the spur gear means is locked in position as indicated, for example, in FIG. 4, or in FIG. 5. Disengaging a worn-out screen cloth for replacement thereof may also be accomplished quite rapidly with leverage first being applied through a wrench or the like to spur gear means 48 in a counterclockwise direction so that the block or pawl may be disengaged therefrom. The spur gear means is thereby released, permitting inner pipe member 32 to rotate in a counterclockwise direction relieving the tension of the screen cloth. If necessary, the spur gear means may be rotated in a clockwise direction to loosen the screen cloth further. After each of the rotatable inner pipe members is thus released, the screen cloth may be easily slid endwise from the frame in the manner in which it was inserted.

It has been found desirable to provide separate segmented inner pipe members 32 spaced lengthways along and within a given outer pipe member 22 so as to allow easier adjustment of tension on the screen cloth and for easier operation of the mechanism by one individual, as well as for lessening the stress applied to individual gears. Thus, the inner pipe member 32 is suitably divided into two sections 32a and 32b, as illustrated in broken away fashion in FIG. 1 and by dashed lines in FIG. 2, which are journaled within each outer pipe member 22. The inward or facing ends of inner pipe member sections are suitably supported upon -a hanger 72 as further illustrated in FIG. 7. This hanger is hung or otherwise secured on the upper portion of wall 18 and extends through circumferential slot 74 in outer pipe member 22 to the ends of inner pipe members 32a and 32b. The lower end 78 of hanger 72 is T-shaped so that it may engage the open ends of both inner pipe member sections. The inner ends of the inner pipe member section are thereby secured from any tendency to fall through slot 30 when the inner pipe member sections are not applying tension to screen cloth 24. In this construction, the hanger 72 may be inserted through slot 74 and then turned so that the lower T-shaped end 78 may engage the inside of both inner pipe sections. The outer ends of the inner pipe sections are suitably supported on hangers comprising a screw 34. Each inner pipe member section is desirably provided wtih at least a pair of rack gear segments spaced along such section for rotating the same.

An alternative embodiment of means for applying leverage for rotating the inner pipe member is illustrated in FIG. 9 wherein an inner pipe member 32' is journaled within outer pipe member 22' forming an integral part of wall 18 of a frame lateral side member. An edge of longitudinal slot 44' in the inner pipe member engages hooked margin 28' of the screen cloth 24. The hooked margin of the screen cloth extends through slot 30' in pipe member 22' in order to reach the inner pipe member. In the FIG. 9 embodiment, the means for applying leverage comprises a double acting hydraulic cylinder means provided with hydraulic feed lines 82 and 84 conveying hydraulic fluid for driving the relatively movable end of the hydraulic piston means comprising actuating rod 86 in either direction longitudinally of the cylinder means in accordance with the direction of flow of hydraulic fluid. The cylinder means is pivoted to wall 18', at 88, and actuating rod 86 is similarly pivoted to radial arm 90 secured as by welding to inner pipe member 32'. Radial arm 90 extends through a peripheral slot 31' in outer pipe member 22'. Upward movement of radial arm 90 rotates inner pipe member 32' in a clockwise direction, placing tension on screen cloth 24, while the reverse operation of the hydraulic cylinder means moves radial arm 90 in the opposite direction for withdrawing such tension.

A further alternative embodiment of the present invention is illustrated in FIGS. 10 and 11. Referring to these figures, the rotatable screen cloth engaging member here comprises a clamping bar 96 which is pivotally secured to wall 98 of a frame lateral side member along an axis 100 extending longitudinally of said frame side member. The edge 102 of the clamping bar remote from axis 100 is directed toward wall 98 and away from the central portion of screen cloth 104 so as to engage hooked margin 106 of the screen cloth.

Wall '98 is provided with an aperture 108 through Which extends a linkage 110 pivotally connected to clamping bar 96 at location 111 intermediate the opposite edges of the clamping bar, and the opposite end of linkage 110 is pivotally connected to an upper portion of a rotatable cam member 112. Cam member 112 is somewhat elliptical in cross section as illustrated in FIG. 10, but has a smaller end 114 which rests upon a shoulder 116 extending from the lower portion of wall 98-. Larger end 118 of cam member 112 is provided with an end bore 120 for receiving a rod 122 insertable therewithin.

Rod 122, which may have an appreciable length, is used as means for applying leverage in a downward direction to cam member 112. Application of such leverage rotates the cam member 112 in a counterclockwise direction through the connection of linkage 110 causing clamping bar 96 to rotate in a clockwise direction with its screen-engaging edge 102 thereby applying tension to screen cloth 104.

The upper portion of cam member 112 is notched as indicated at 124 to receive a pin 126 which may be depressed within one of the notches by downward pressure on actuating rod 128 against the tension of spring 130. Pin 126 is pivoted to wall 98 at 127, and acts as a detent means. Thus, when sufiicient pressure is applied to rod 122 to correctly tension screen cloth 104, actuating rod 128 may be depressed to insert pin 126 in one of the notches and lock the cam member against rotation. The clamping bar 96 is thereby also secured until such time as it is desired to replace the screen cloth. Then, rod 122 is reinserted in bore 120' and urged downwardly whereby piri 126 will be urged upwardly by spring 130 so that the cam member will be allowed to rotate in a clockwise direction for releasing the screen cloth. As in the previous embodiments, the screen cloth can be installed and replaced with a minimum of effort and in a minimum number of operations.

As illustrated in FIG. 11, cam member 112 suitably extends for a short distance along wall 98 of a frame lateral side member, while it is understood that clamping bar 96, on the other hand, extends for a greater distance along the inside of the apparatus frame for engaging the extended hooked margin of the screen cloth. Desirably,

a plurality of cam members 112 are operatively connected to one such clamping bar at spaced locations therealong.

While I have shown and described several embodiments of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from my invention in its broader aspects. I therefore intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

I claim:

1. Screen tightening apparatus for supporting and tightening a heavy screen cloth having a hooked margin on a lateral side, said apparatus comprising:

a frame within which said screen cloth is substantially horizontally and centrally positionable, a first rotatable pipe member having a longitudinal axis disposed along and substantially parallel with a lateral side of said frame adjacent the position of a hooked margin of said screen cloth,

an outer pipe member secured to said frame substantially concentrically with said first pipe member, within which said first pipe member is journaled,

each of said pipe members having a longitudinal slot,

wherein an edge of the slot in the first pipe member is directed outwardly of said frame and is engageable with a hooked margin of said screen cloth, and wherein the slot in the outer pipe member provides access to the first pipe member through which said screen cloth may extend, the slot in the outer pipe member opening horizontally and having a width so the screen cloth may extend horizontally therethrough for engagement of the margin thereof with the edge of the slot in the first pipe member in various positions of tension,

means for applying leverage for rotating said first pipe member to rotate the said slot in the first pipe member so that the screen engaging edge thereof is urged toward said hooked margin for placing said hooked margin under tension, and means for locking said first pipe member in tensioning position.

2. Screen tightening apparatus for supporting and tightening a heavy screen cloth having a hooked margin on each lateral side, said apparatus comprising;

a frame within which said screen cloth is substantially horizontally and centrally positionable,

first rotatable pipe members having longitudinal axes disposed along and substantially parallel with either lateral side of said frame adjacent the position of hooked margins of said screen cloth,

outer pipe members secured to said frame substantially concentrically with said first pipe members, within which said first pipe members are journaled,

each of said pipe members having a longitudinal slot,

wherein an edge of the slot in each first pipe member is directed outwardly of said frame and is engageable with the hooked margin of said screen cloth, and wherein the slot in an outer pipe member provides access to a first pipe member through which said screen cloth may extend, the slots in the outer pipe members substantially horizontally facing one another across the frame so that the screen cloth may extend horizontally therethrough, the slots in the outer pipe members having widths for allowing horizontal passage of the screen cloth in positions of selectively greater tension, means for applying leverage for rotating said first pipe members to rotate the said slot in each first pipe member so that the screen engaging edge thereof is urged towards a said hooked margin for placing said hooked margin under tension, and means for locking said first pipe members in tensioning position.

3. The apparatus according to claim 2 wherein said means for applying leverage includes gear means mounted on said first pipe members.

4. The apparatus according to claim 2 including bydraulic piston means, one end of said hydraulic piston means being secured to said frame and the opposite relatively movable end of said hydraulic piston means being pivotally secured to a said first pipe member for rotating such first pipe member with respect to an outer pipe member.

5. The apparatus according to claim 2 wherein the slots in the outer pipe members substantially face each other horizontally across the frame and extend angularly downward so that rotation of the first pipe members pulls the margins of said screen cloth outwardly and downwardly while maintaining a substantially horizontal attitude of said screen cloth. I

6. The apparatus according to claim 5 further including hanger means extending downwardly from each outer pipe member and supportably engaging the corresponding inner pipe member.

7. Screen apparatus for supporting and tightening a screen cloth having an upturned hooked margin at opposite lateral edges thereof, said apparatus comprising:

a frame within which said screen cloth is substantially horizontally and centrally positionable, said frame including cross members and a plurality of risers mounted on said cross members for supporting the central portion of said screen cloth,

said frame having lateral side members joined to said cross members and each including a pipe member extending longitudinally along a lateral side member adjacent a hooked margin of said screen cloth, each pipe member being provided with a'longitudinal slot facing inwardly of said frame toward said screen cloth and downwardly for receiving the up turned hooked margin of said screen cloth therethrough,

an inner pipe member rotatably journaled in each said first mentioned pipe member, each said inner pipe member also being provided with a longitudinal slot, wherein said longitudinal slot of each said inner pipe member provides an edge for engaging said upturned margin of said screen cloth in hooked relation therewith,

plural rack gear segments joined to each said inner pipe member at the periphery thereof toward the outside of said lateral side members, said first mentioned pipe members having apertures at the location of said rack gear segments so that said rack gear segments may extend therethrough, a spur gear means engaging each of said rack gearsegments wherein each said spur gear means is mounted on a lateral side member for rotational engagement with the corresponding rack gear segment, each said spur gear means being provided with a lever-engageable means for turning said spur gear means,

and means for locking said spur gear means in a desired rotational position.

8. The apparatus according to claim 7 wherein said means for locking said spur gears in a desired position comprises a pawl pivotally attached to a frame side member for engaging said spur gear means and holding the same in a position applying tension to said screen cloth.

9. The apparatus according to claim 7 further including hangers for suspending said inner pipe members within said first mentioned pipe members.

10. The apparatus according to claim 7 wherein each said first mentioned pipe member is located with the diameter thereof substantially coinciding with the extended location of a lateral side member wall, said apparatus further including cover means joined to each of said lateral side members above the apertures in said first mentioned pipe members and extending inwardly from the said wall of each said lateral side member to cover said apertures.

11. The apparatus according to claim 7 wherein each of said first mentioned pipe members houses a plurality of inner pipe members journaled therewithin and spaced lengthways within a said first mentioned pipe member, each of said inner pipe members being provided with at least a pair of said rack gear segments spaced therealong for rotating the same.

12. Screen tightening apparatus for supporting and tightening screen cloth having a hooked margin, said apparatus comprising:

a frame within which said screen cloth is substantially horizontally and centrally positionable, 10 a first rotatable pipe member having a longitudinal axis disposed along and substantially parallel with a lateral side of said frame adjacent the position of a hooked margin of said screen cloth, an outer pipe member secured to said frame su-bstantially concentrically with said first pipe member, within which said first pipe member is journaled,

each of said pipe members having a longitudinal slot,

wherein an edge of the slot in the first pipe member is directed outwardly of said frame and is engageable with the hooked margin of said screen cloth, and wherein the slot in the outer pipe member provides access to the first pipe member through which said screen cloth may extend,

said first pipe member being provided with gear means mounted thereon for rotation therewith and wherein said outer pipe member is apertured to receive said gear means therethrough so that said gear means is driveable from outside said outer pipe member, said apparatus including spur gear means rotatably mounted on said frame and in engagement with said first mentioned gear means for rotating said first pipe member, said spur gear means being adapted to receive a lever arm for rotating the same.

13. The apparatus according to claim 12 further including means for locking said first pipe member comprising means for locking said spur gear means in desired position for thereby holding the tension applied to said screen cloth.

14. Screen tightening apparatus for supporting and tightening screen cloth having a hooked margin, said apparatus comprising:

a frame within which said screen cloth is substantially horizontally and centrally positionable,

a rotatable member having a longitudinal axis disposed along and substantially parallel with a lateral side of said frame adjacent the position of a hooked margin of said screen cloth, said rotatable member comprising a clamping bar pivotally secured to said frame and having a longitudinal screen engaging edge located remotely from the axis about which said clamping bar is rotatable and directed outwardly toward the location of said hooked margin of said screen cloth so that said edge is engageable with said hooked margin,

a cam member rotatable against said frame about an axis parallel to the pivotal axis of said clamping bar,

a movable linkage joining said cam member to said clamping bar at points on said member and bar removed from the axes thereof,

means for applying leverage to said cam member to rotate said cam member and thereby rotate said clamping bar through movement of said linkage to place said hooked margin of said screen cloth in tension within said frame,

and detent means for selectively locking the position of said cam member for thereby locking the clamping bar in tensioning position.

References Cited UNITED STATES PATENTS 780,826 1/ 1905 Sneide 209-403 2,000,426 5/ 1935 Symons 209403 2,279,042 4/ 1942 Harrington 209403 2,498,716 2/1950 Seide 160378 2,848,109 8/1958 Pruitt 209319 X 3,008,410 11/1961 Bryer 101415.1 3,203,548 8/ 1965 Roubal 2i09403 X 3,346,114 10/ 1967 Hoyt 209-403 3,382,799 5/1968 Luehrs 101415.1

FOREIGN PATENTS 711,097 6/1965 Canada.

TIM R. MILES, Primary Examiner U.S. Cl. X.R. 

